I recently had the same issue where the WordFense plugin disappears from WP admin. I host on GoDaddy. I also noticed when I tried to update any of the plugins that needed updated I would get the following message …
Update Failed: <!DOCTYPE HTML PUBLIC “-//IETF//DTD HTML 2.0//EN”> 503 Service Unavailable Service Unavailable The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later. Apache Server at ****** Port 443
I manually removed all of the WordFense files (at first thinking they were compromised) and I still get the error message. I am going to reach out to GoDaddy and see what they can tell me. I am not sure this is a WordFence issue (since it is now gone) but that fact that the plugin disappeared from admin seems somewhat related.